Trichoderma asperellum and T. asperelloides: Comparative Genomic Study for Genes Implicated in Biocontrol and Biofertilizer Activities

Trichoderma asperellum and T. asperelloides are two cryptic species that have potential for use as biocontrol and biofertilizer (B&B) agents. Comparison of the reference genomes of the two species revealed that each species had seven chromosomes, but Trichoderma asperellum has about 1000 more genes than T. asperelloides. The number of genes coding for chitinases, cellulases, xylanases, secreted proteases, and genes involved in soil and plant health was slightly greater in T. asperellum than in T. asperelloides. Moreover, T. asperellum had five more genes than T. asperelloides involved in the synthesis of secondary metabolites like peptaibols and siderophores. The B&B genes were distributed on all the chromosomes. No duplicate genes were found for any of the enzymes searched. The investigation also revealed that T. asperellum had 15 copies of the internal transcribed spacer (ITS) region of ribosomal DNA compared to only seven copies in T. asperelloides. Further transcriptomic, proteomic, and efficacy studies are needed to determine the impact of the missing genes in T. asperelloides on its B&B activities compared to those of T. asperellum. The search for B&B genes in T. asperelloides was hindered by the lack of annotation for the genome. Thus, comparison only involves B&B genes searched in T. asperellum and whether homologs to the genes were available or missing in T. asperelloides. A comparison between additional strains of the two species is essential to show whether the data in this study apply to all intraspecies strains of the two species.